1. Field of the Invention
The present invention relates to a thin-film magnetic recording head for use in, for example, a flying magnetic head, and more particularly, to a thin-film magnetic head which is capable of reducing the track width, preventing write fringing, and reducing magnetic saturation, and a production method for the head.
2. Description of the Related Art
FIG. 12 is a partial front view showing the structure of a conventional thin-film magnetic head (inductive head), and FIG. 13 is a partial sectional view of the thin-film magnetic head, taken along line XIIIxe2x80x94XIII in FIG. 12, as viewed from the directions of the arrows.
Referring to FIGS. 12 and 13, a lower core layer 1 is made of a magnetic material, such as permalloy, and a nonmagnetic gap layer 7 is formed thereon.
As shown in FIG. 13, a coil layer 5 is formed on the gap layer 7 via an organic insulating layer 4 made of a polyimide, a resist, or the like.
An organic insulating layer 6 made of a polyimide, a resist, or the like is formed on the coil layer 5, and an upper core layer 3 made of a magnetic material, such as permalloy, is formed on the organic insulating layer 6.
As shown in FIG. 12, a leading end portion 3a of the upper core layer 3 opposes the lower core layer 1 via the gap layer 7, and the width thereof is limited to a track width Tw. A base end portion 3b of the upper core layer 3 is magnetically connected to the lower core layer 1.
In the inductive head shown in FIGS. 12 and 13, when a recording current is applied to the coil layer 5, a recording magnetic field is induced in the lower core layer 1 and the upper core layer 3, and a magnetic signal is recorded on a recording medium, such as a hard disk, by a leakage magnetic field from between the leading end portion 3a of the upper core layer 3 and the lower core layer 1.
With future increase in recording density, it is necessary to reduce the track width.
As described above, the track width Tw is regulated by the width of the leading end portion 3a of the upper core layer 3 (see FIG. 12). The upper core layer 3 is formed by so-called flame plating.
In flame plating, a resist layer is first applied over the entire surface where the upper core layer 3 is to be formed, and a pattern of the upper core layer 3 is formed on the resist layer by exposure and development. Subsequently, the pattern is plated with a magnetic material, and the resist layer is removed, thereby finishing the upper core layer 3 having the shape shown in FIGS. 12 and 13.
The resolution of the resist layer is greatly concerned with the wavelength of the light used for exposure and development. The resolution can be improved by shortening the wavelength.
However, the resolution has, of course, its limits, and it is impossible to perform patterning when the track width Tw regulated by the width of the leading end portion 3a of the upper core layer 3 is smaller than the resolution limit. Accordingly, it is difficult for the inductive head with the structure shown in FIGS. 12 and 13 to reduce the track width with future increase in recording density.
When the track width Tw is reduced, the volume of the leading end portion 3a of the upper core layer 3 is decreased, and magnetic saturation becomes pronounced with an increase in recording frequency. This degrades the recording characteristics.
In the inductive head shown in FIGS. 12 and 13, a leakage magnetic field produced between the lower core layer 1 and the leading end portion 3a of the upper core layer 3 protrudes from the track width Tw, that is, so-called write fringing is prone to occur.
When write fringing occurs, the track position on a recording medium cannot be detected precisely, an tracking servo error is caused, and the recording characteristics are degraded.
Write fringing is prone to be caused when the lower core layer 1 protrudes from the track width Tw, as shown in FIG. 12, and the distance between the protruding portion of the lower core layer 1 and the leading end portion 3a of the upper core layer 3 is short.
Japanese Unexamined Patent Application Publication No. 10-143817 discloses the structure of an inductive head which effectively prevents write fringing described above.
However, the invention disclosed in the above publication makes the production procedure troublesome. That is, the production procedure includes a process of removing the portion of the gap layer 7 protruding from the track width Tw shown in FIG. 12. While an appropriate distance can be formed between the lower core layer 1 and the leading end portion 3a of the upper core layer 3 by etching the surface of the lower core layer 1, which is exposed by removing the portion of the gap layer 7, by ion milling, magnetic powders adhere to both side faces of the leading end portion 3a and the like. A process of removing the adhering powders is also required.
Furthermore, the disclosed invention does not allow reduction in track width and prevention of magnetic saturation.
The present invention solves to the above conventional problems, and an object of the present invention is to provide a thin-film magnetic head which is capable of reducing the track width, preventing write fringing, and reducing magnetic saturation, and a production method for the head.
According to an aspect of the present invention, there is provided a thin-film magnetic head including upper and lower core layers, and a track width regulating section disposed between the upper and lower core layers so as to have a width shorter than those of the upper and lower core layers, wherein the track width regulating section is composed of a lower pole layer connected to the lower core layer, an upper pole layer connected to the upper core layer, and a gap layer disposed between the lower pole layer and the upper pole layer, or is composed of an upper pole layer connected to the upper core layer and a gap layer disposed between the upper pole layer and the lower core layer, and an inclined face is formed on the upper surface of the lower core layer extending on both sides of the track width regulating section so as to be inclined away from the track width regulating section in the track width direction in order to gradually increase the distance from the upper core layer.
As described above, the track width regulating section, whose width in the track width direction is regulated by the track width, is formed between the upper core layer and the lower core layer. The upper pole layer magnetically connected to the upper core layer is formed in the track width regulating section. Since the inclined face inclined in the direction away from the upper core layer is formed on the upper surface of the lower core layer extending from both sides of the track width regulating section, an appropriate distance is ensured between the upper pole layer and the lower core layer, and write fringing can be effectively prevented.
The width of the upper core layer formed on the upper pole layer is larger than the track width. This adequately reduces magnetic saturation adjacent to the leading end portion of the upper core layer.
In a production method which will be described later, the width of the track width regulating section (=the track width) can be made smaller than the resolution obtained by the wavelength of the light used for exposure and development of a resist, which allows the track width to be reduced with future increase in recording density.
Preferably, the track width to be regulated by the width of the track width regulating section is 0.4 xcexcm or less. This value is smaller than the resolution obtained when the i-line is used during exposure and development of the resist. More preferably, the track width is set at 0.2 xcexcm or less.
Preferably, an inclination angle xcex81 of the inclined face formed on the upper surface of the lower core layer with respect to the track width direction ranges from 2xc2x0 to 10xc2x0. Within this range, it is possible to adequately suppress write fringing and to sufficiently maintain the shielding function of the lower core layer.
According to another aspect of the present invention, there is provided a thin-film magnetic head including upper and lower core layers having a width larger than the track width, and a track width regulating section disposed between the upper and lower core layers so as to have a width limited to the track width, wherein the track width regulating section is composed of a lower pole layer connected to the lower core layer, an upper pole layer connected to the upper core layer, and a gap layer disposed between the lower pole layer and the upper pole layer, or is composed of an upper pole layer connected to the upper core layer and a gap layer disposed between the upper pole layer and the lower core layer, and the track width regulated by the track width regulating section is 0.4 xcexcm or less.
As described above, the track width regulating section, whose width in the track width direction is limited to the track width, is formed between the lower core layer and the upper core layer. Since the width of the upper core layer is larger than the track width, the volume of the upper core layer adjacent to the leading end thereof is increased, and magnetic saturation is adequately reduced.
In a production method which will be described later, the width of the track width regulating section (=the track width) can be made smaller than the resolution obtained by the wavelength of the light used for exposure and development of a resist.
In particular, the track width is set at 0.4 xcexcm or less, and this value is smaller than the resolution limit obtained when the i-line is used for exposure and development. More preferably, the track width is set at 0.2 xcexcm.
Preferably, an inclined face is formed on the upper surface of the lower core layer extending on both sides of the track width regulating section so as to be inclined away from the track width regulating section in the track width direction to gradually increase the distance from the upper core layer.
While the upper pole layer magnetically connected to the upper core layer is formed in the track width regulating section, the above-described configuration allows an appropriate distance between the upper pole layer and the lower core layer and thereby effectively suppresses write fringing.
Preferably, an inclination angle xcex81 of the inclined face formed on the upper surface of the lower core layer with respect to the track width direction ranges from 2xc2x0 to 10xc2x0.
Preferably, the height of the track width regulating section ranges from 2 xcexcm to 10 xcexcm. Within this range, an appropriate distance is ensured between the lower core layer and the upper pole layer, and write fringing is suppressed. Furthermore, the height of the upper pole layer is increased, and magnetic saturation is seldom caused even when the recording density is increased. Furthermore, the track width regulating section can be easily formed.
Preferably, the gap layer is made of a nonmagnetic metal material which can be plated. The nonmagnetic metal material may include one or more among NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.
According to a further aspect of the present invention, there is provided with a thin-film magnetic head production method including the steps of (a) forming a resist layer on a lower core layer and forming, in the resist layer, a groove having a predetermined width and a predetermined length from the surface opposing a recording medium in the height direction; (b) forming, in the groove, a track width regulating section composed of a lower pole layer, a nonmagnetic gap layer, and an upper pole layer stacked in order or composed of a nonmagnetic gap layer and an upper pole layer stacked in order; (c) removing the resist layer; (d) limiting the width of the track width regulating section to the track width by etching both side faces of the track width regulating section in the track width direction; (e) forming an inclined face on the upper surface of the lower core layer extending on both sides of the track width regulating section so as to be inclined away from the track width regulating section to gradually increase the distance from the upper core layer; and (f) forming an upper core layer having a width larger than the track width on the track width regulating section.
As described above, the resist layer is first applied on the lower core layer, and a pattern of the track width regulating section is formed on the resist layer by exposure and development. The width of the pattern to become the track width regulating section is greatly concerned with the wavelength of the light used for exposure and development. For example, when the i-line (the wavelength thereof=365 nm) is used, the width can be reduced to approximately 0.4 xcexcm.
The value of 0.4 xcexcm is the resolution limit obtained when the i-line is used, and a pattern having a width smaller than 0.4 xcexcm cannot be formed on the resist layer.
Accordingly, after the track width regulating section is formed in the pattern of the resist layer, the width thereof (=the track width) is further reduced by etching both side faces of the track width regulating section in the track width direction. For this reason, for example, when the width of the pattern formed on the resist layer is approximately 0.4 xcexcm that is the resolution limit obtained by the i-line used for exposure and development, the width of the track width regulating section can be limited to 0.4 xcexcm or less. In this way, the present invention allows the width of the track width regulating section (=the track width) to be smaller than the resolution obtained by the i-line.
The production method includes the step of forming an inclined face on the upper surface of the lower core layer extending from both ends of the track width regulating section so as to be inclined away from the track width regulating section to gradually decrease the thickness of the lower core layer. This adequately prevents write fringing.
Since the upper core layer having a width larger than the track width is formed on the upper pole layer constituting the track width regulating section by, for example, flame plating, it is possible to increase the volume of the upper core layer adjacent to the leading end thereof and to adequately reduce magnetic saturation.
Preferably, the step (d) of limiting the width of the track width regulating section and the step (e) of forming the inclined face are simultaneously performed by ion milling. This simplifies the production method.
Preferably, the ion irradiation angle xcex82 for ion milling ranges from 45xc2x0 to 75xc2x0 with respect to the direction in parallel with the height direction of the track width regulating section. More preferably, the ion irradiation angle xcex82 ranges from 55xc2x0 to 70xc2x0.
The above ion irradiation angle xcex82 makes it possible to reduce the track width without extremely reducing the height of the upper pole layer, as shown by the experimental result, which will be described later. Moreover, the inclined face can be easily formed on the upper surface of the lower core layer by setting the ion irradiation angle 02 at the above value.
Preferably, the track width to be regulated by the track width regulating section in the above step (d) is set at 0.4 xcexcm or less.
The track width set at 0.4 xcexcm or less can be made smaller than the resolution limit obtained when the i-line is used for exposure and development of a resist. More preferably, the track width is set at 0.2 xcexcm or less.
Preferably, the inclined face formed on the upper surface of the lower core layer in the step (e) has the inclination angle xcex81 ranging from 2xc2x0 to 10xc2x0 with respect to the track width direction.
By setting the ion irradiation angle xcex82 for ion milling within the range of 45xc2x0 to 75xc2x0, it is possible to make the track width 0.4 xcexcm or less and to form the inclined face on the upper surface of the lower core layer at the inclination angle xcex81 ranging from 2xc2x0 to 10xc2x0 with respect to the track width direction.
Preferably, the gap layer constituting the track width regulating section is formed by plating together with the pole layer. This allows the pole layer and the gap layer to be successively formed by plating.
Preferably, a nonmagnetic metal material to be plated to form the gap layer includes one or more among NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.